JP2002040228A - Cholesteric liquid crystal color filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost cholesteric liquid crystal color filter excellent in impact resistance and in color purity which can be suitably used for a LCD using a resin cell, which is composed of a resin (plastic) substrate (cell substrate) and which can be easily formed at the temperature as low as <=100 deg.C without causing problems such as deformation of the substrate. SOLUTION: The cholesteric liquid crystal color filter is obtained by forming a layer containing a cholesteric liquid crystal composition on a resin substrate. Preferably, the cholesteric liquid crystal composition contains a polymerizable cholesteric liquid crystal compound, photoreactive chiral compound and polymerization initiator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cholesteric liquid crystal color filter obtained by patterning a cholesteric liquid crystal composition and used for a display device such as an LCD suitable for a portable terminal or a small personal computer.

[0002]

2. Description of the Related Art Color liquid crystal displays (color LCs)
Color filters used in display devices such as D) include:
In general, each pixel of red (R), green (G), and blue (B) is formed by forming a black matrix for improving display contrast in a gap between the pixels. Heretofore, color filters in which a pigment is dispersed in a resin or dyes are dyed are mainly used, and are generally formed on a glass substrate constituting a liquid crystal cell. However, in recent years, with the rapid spread of mobile devices such as mobile phones and portable terminals and small personal computers, etc., they have been used outdoors because of their ease of use and excellent portability. Many damage claims such as breakage of glass substrates and the like have been generated.

Along with the above-mentioned situation, recently, in a portable terminal of a communication device such as a cellular phone, a small personal computer, and the like, a resin is used as a substrate of a display portion (hereinafter, sometimes referred to as a “cell substrate”). Substrate (plastic substrate)
LCDs have been adopted. This has the advantage that, due to the characteristics of plastic, it is difficult to break even if it is accidentally given an impact during portable use, and even in the market there is a tendency for breakage claims to be overwhelmingly reduced.

Currently, monochrome LCDs are widely used as LCDs using a plastic substrate, but color display LCDs are still under examination. Challenges. That is, it is the point of light transmittance and color purity of the color filter. Hitherto, in the production of color filters, production methods such as a printing method, a pigment dispersion method, and an electrodeposition method have been used. But,
The printing method has a drawback that the resolution of pixels is low and it is difficult to form a high-resolution image pattern. Therefore, in recent years, the pigment dispersion method has become the mainstream.

However, in the pigment dispersion method, it is required that the color filter does not contain impurities such as ions because the color filter is in direct contact with the liquid crystal. To avoid this, it is necessary to mix a binder and a monomer component which solidify particularly under high heat and harden them by baking at a high temperature of 200 ° C. or more. As a result, a normal image display has been ensured without impairing the switching function of the liquid crystal even when the liquid crystal contains many impurities.
As described above, high-temperature baking of about 200 ° C. or more is indispensable, and under such temperature, a plastic substrate cannot be used due to warpage or deformation, and as a transparent substrate that can be used for a liquid crystal cell into which liquid crystal is introduced, it is practically used. Other than glass substrates could not be used. Therefore, in order to avoid breakage of the glass substrate as much as possible, a thick plastic substrate was attached to the surface of the glass substrate to commercialize the product, but the number of damage claims did not decrease.

On the other hand, there is an electrodeposition method as a method of coloring a plastic cell substrate at a low temperature. According to this method, a color filter can be formed without affecting properties such as warpage or deformation of a plastic (resin), and it has already been commercialized and a certain market has been formed. However, the electrodeposition method has a problem that the production process is complicated and liquid management is difficult, and the formed color filter is remarkably inferior in color purity so that only a dull color display can be performed.

[0007] Recently, there is a particularly high demand for the transmittance and color purity of color filters in liquid crystal display (LCD) panels. Accordingly, even small portable devices are no exception, and there is a demand for improved color purity.
However, as described above, at present, a color filter that is formed on a plastic (resin) cell substrate without causing a problem such as deformation and has excellent color purity has not yet been provided.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, the present invention provides a cholesteric liquid crystal color filter which is suitably used for an LCD using a resin cell, is made of a resin (plastic) substrate (cell substrate), has excellent impact resistance, and has excellent color purity. Aim. Another object of the present invention is to provide a low-cost cholesteric liquid crystal color filter that can be easily formed on a resin substrate (cell substrate) at a low temperature of 120 ° C. or less without any trouble such as deformation of the substrate. Aim.

[0009]

Means for Solving the Problems The present inventors have studied the above-mentioned conventional problems when a plastic substrate is used as a cell substrate, and as a result, have found that the color purity of a color filter film is improved and uniformity is ensured. And process temperature is 1
It has been found that a method using a cholesteric liquid crystal compound and a photoreactive chiral compound is useful for realizing a reduction in the number of manufacturing steps at a low temperature of 20 ° C. or less. In this method, when a liquid crystal composition containing a photoreactive chiral compound is irradiated with light having a reaction wavelength of the chiral compound in a pattern, the reaction of the chiral compound proceeds in accordance with the intensity of the irradiation energy, and the reaction of the liquid crystal compound proceeds. Since the helical pitch (helical twist angle) changes, the selective reflection color is formed for each pixel only by pattern exposure having a light amount difference. That is, the cholesteric liquid crystal composition is irradiated with light imagewise in a state where the composition is heated to about 100 ° C. and patterned, and then the patterned cholesteric liquid crystal compound is irradiated again with light or at 120 ° C.
By fixing by the following heating, a cured film having a high film strength and functioning as a color filter (polarized light utilization type) can be formed.

[0010] The color filter mainly composed of the cholesteric liquid crystal uses a selective reflection characteristic of reflecting a certain amount of light and transmitting an image other than the cholesteric liquid crystal to display an image. In terms of purity, it has more excellent performance than a light absorption type color filter containing a pigment or the like produced by a pigment dispersion method or an electrodeposition method. In addition, when a color filter is manufactured, the heating temperature can be reduced to 120 ° C. or lower, and if a mask having a different amount of transmitted light is used, it can be completed in one mask exposure, and the process can be simplified. .

On the other hand, the cholesteric liquid crystal color filter has a drawback that it has a large viewing angle dependency, but it does not hinder the use such as a portable terminal which can be seen only from the front by one person, and is not suitable as a product. It is not a problem.

The means for solving the above problems are as follows. That is, <1> a cholesteric liquid crystal color filter, wherein a layer containing a cholesteric liquid crystal composition is provided on a resin substrate.

<2> The cholesteric liquid crystal composition according to <1>, wherein the composition comprises at least one polymerizable cholesteric liquid crystal compound, at least one photoreactive chiral compound, and at least one polymerization initiator. It is a cholesteric liquid crystal color filter of the description.

<3> The cholesteric liquid crystal color filter according to <1> or <2>, wherein the polymerizable cholesteric liquid crystal compound has a functional group which is polymerized and cured in response to ultraviolet light in the same molecule.

<4> At least one step of patterning the cholesteric liquid crystal composition provided on the resin substrate by imagewise exposing with the first light and then photopolymerizing and curing with the second light. <1> obtained by a method for manufacturing a cholesteric liquid crystal color filter including a step
A cholesteric liquid crystal color filter according to any one of <1> to <3>.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A cholesteric liquid crystal color filter according to the present invention has a cholesteric liquid crystal color filter formed on a resin (plastic) cell substrate. Hereinafter, the cholesteric liquid crystal color filter of the present invention will be described.

The cholesteric liquid crystal color filter of the present invention is provided with a layer containing a cholesteric liquid crystal composition on a resin-made cell substrate. If necessary, two or more layers may be laminated. Another layer (film) such as a film may be provided. A specific manufacturing method will be described later.

<Substrate> As the substrate (cell substrate),
The substrate can be appropriately selected from known resin (plastic) substrates, and specifically, the following substrates are suitable. In the case of a transmission type LCD for a liquid crystal display element, those having high transmittance of visible light are preferable, for example, acrylic resin such as polymethyl methacrylate, polycarbonate such as polydiethylene glycol bisallyl carbonate, polyether sulfone, cellulose acetate, and amorphous. Examples thereof include polyolefin, polyester, epoxy, unsaturated polyester, and polystyrene. In order to prevent expansion and contraction and deformation due to heat, a resin in which fine particles such as silicon oxide or barium sulfate or inorganic fibers such as glass fiber are dispersed in the above resin can be used.

In the case of a reflective or transflective LCD (a transflective LCD in which an internal lamp is turned on only when used in a dark room where incident light is low), a colored resin having a low visible light transmittance is used. Plates are preferred. In particular, by mixing carbon black or carbon fiber or other organic or inorganic pigments, using a resin plate colored black,
In addition, by adopting a configuration in which a reflective film is provided in the pixel portion to selectively reflect only the incident light of the pixel portion and absorb the incident light between the pixels to the black resin substrate, the contrast can be improved.

Particularly, as described in JP-A-6-43444, a resin substrate in which a gas barrier layer is provided on the above various substrates is preferable. In general, a resin (plastic) substrate has high gas permeability, so that after a liquid crystal composition is encapsulated to produce an LCD, display defects due to air intrusion into the liquid crystal cell due to changes in humidity and aging are caused. In some cases, the liquid crystal cell is broken or the solvent resistance is poor. From the viewpoint of avoiding these situations, it is preferable that a gas barrier layer having a high gas barrier property is provided on one or both surfaces of the resin substrate.

The thickness of the resin substrate is 20 to 1
000 μm is preferred, and 50 to 500 μm is more preferred. When the thickness is less than 20 μm, sufficient strength cannot be maintained, and warpage or bending occurs, and high-precision patterning may be difficult.
In some cases, the rigidity of the substrate becomes too high, the local pressure at the time of bonding increases, and a uniform cell gap cannot be obtained.

By using a resin substrate instead of a conventional glass substrate as the cell substrate, the impact resistance can be greatly improved. In addition, since it is lighter in weight than a glass substrate, it is suitable for a small portable device.

<Cholesteric Liquid Crystal Composition> The cholesteric liquid crystal composition (hereinafter sometimes simply referred to as “liquid crystal composition”) comprises at least one polymerizable cholesteric liquid crystal compound and at least one photoreactive chiral compound. Compound, and contains at least one polymerization initiator, if necessary, a binder resin, a solvent, a surfactant, a polymerization inhibitor, a thickener, a pigment such as a pigment, an ultraviolet absorber, a gelling agent Etc. may be included.

(Cholesteric liquid crystalline compound) In the present invention, a polymerizable cholesteric liquid crystalline compound is used as the liquid crystal compound. The cholesteric liquid crystal compound has a refractive index anisotropy Δn of 0.10 to 0.40 and is appropriately selected from polymerizable liquid crystal compounds having a polymerizable group or a crosslinkable group introduced into a terminal of a liquid crystal molecule. be able to.
While in the liquid crystal state at the time of melting, it can be used as a solid phase by, for example, aligning by using an alignment substrate that has been subjected to an alignment treatment such as a rubbing process, and cooling and polymerizing and curing it as it is. it can. That is, when the liquid crystal compound is efficiently polymerized in the aligned state, its reactivity is extremely high, so that a tough film can be formed.

Examples of the polymerizable cholesteric liquid crystalline compound include, for example, UV curable polymerizable in response to ultraviolet rays.
A liquid crystal compound in which a curable functional group (for example, an acrylate group) is introduced into the molecule of the cholesteric liquid crystal compound is preferably used. If this is cured by irradiating ultraviolet rays, a color filter having a high film strength at a low temperature of 120 ° C. or less can be produced.

Specific examples of the cholesteric liquid crystalline compound include the following compounds. However, the present invention is not limited to these.

[0027]

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[0028]

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[0029]

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In the above formula, n represents an integer of 1 to 1000. In each of the above exemplified compounds, those in which the side chain linking group is changed to the following structure can also be mentioned as suitable compounds.

[0031]

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Among the above, the cholesteric liquid crystal compound is preferably a cholesteric liquid crystal compound having a polymerizable group or a crosslinkable group in the molecule from the viewpoint of excellent curability and ensuring the heat resistance of the layer.

The content of the cholesteric liquid crystal compound is preferably from 30 to 98% by weight, more preferably from 50 to 95% by weight, based on the solid content of the liquid crystal composition. If the content is less than 30% by weight, the orientation may be insufficient and a desired selective reflection color may not be obtained.

(Photoreactive Chiral Compound) The photoreactive chiral compound is a compound capable of changing the helical pitch induced in the cholesteric liquid crystal composition by light irradiation (ultraviolet light to visible light to infrared light). The site (molecular structural unit) includes a chiral site and a site that undergoes a structural change by light irradiation. These sites are preferably contained in one molecule. In the present invention, in addition to the photoreactive chiral compound, a chiral compound that does not react with light, such as a chiral compound having a large temperature dependence of torsion, can be used in combination.

The chiral compound preferably has a light-sensitive peak wavelength longer than the light-sensitive peak wavelength of the polymerization initiator in order to improve patterning sensitivity.
The chiral compound preferably has a large force for inducing the helical structure of the cholesteric liquid crystal composition. For this purpose, it is preferable that the chiral site is located at the center of the molecule and the periphery thereof has a rigid structure. Is 30
0 or more is preferable. In order to increase the inductive force of the helical structure by light irradiation, it is preferable to use a material having a large degree of structural change by light irradiation, and to make the chiral part and the part that causes structural change by light irradiation close to each other.

Further, a chiral compound having high solubility in a cholesteric liquid crystal compound is preferable, and a compound having a solubility parameter SP value close to that of a liquid crystal polymerizable monomer is more preferable. When the chiral compound has a structure in which one or more polymerizable bonding groups are introduced, the heat resistance of the formed liquid crystal composition film (color filter) can be improved.

Examples of the structure of the photoreactive portion whose structure is changed by light irradiation include a photochromic compound (Kingo Uchida,
Masahiro Irie, Chemical Industry, vol. 64, p. 640, 1
999, Kingo Uchida, Masahiro Irie, Fine Chemical, v
ol. 28 (9), p.15, 1999). Hereinafter, specific examples will be described, but the present invention is not limited thereto.

[0038]

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In the formula, R ¹ and R ² represent an alkyl group, an alkoxy group, an anenyl group or an acryloyloxy group.

As a chiral site, by light irradiation,
Degradation, addition reaction, isomerization, dimerization reaction and the like may occur, and the structure may be irreversibly changed. Further, as the chiral site, for example, an asymmetric carbon in which different groups are bonded to four bonds, such as a carbon atom marked with * of the compound exemplified below, corresponds to (the chemistry of liquid crystal, No. .22, Hiroyuki Nohira, Chemistry Review, p.73,199
4).

[0041]

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As the photoreactive chiral compound having both a chiral site and a photoisomerization unit, the following compounds can be exemplified.

[0043]

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Further, a photoreactive chiral compound represented by the following general formula (I) or (II) is also preferable.

[0045]

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In the general formulas (I) and (II), R represents a hydrogen atom, an alkoxy group having 1 to 15 carbon atoms, a total of 3 to 3 carbon atoms.
15 represents an acryloyloxyalkyloxy group and a methacryloyloxyalkyloxy group having 4 to 15 carbon atoms in total.

Hereinafter, as specific examples of the compound represented by the general formula (I), examples of the R group (exemplified compounds (1) to (1)
5))), but the present invention is not limited to these.

[0048]

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The total content of the chiral compound in the cholesteric liquid crystal composition is not particularly limited and can be appropriately selected, but is preferably about 2 to 30% by weight.

(Polymerization Initiator) In order to fix the helical structure after changing the torsional force of the liquid crystal due to light irradiation and to further improve the strength of the liquid crystal composition after the fixation, the polymerization reaction due to the unsaturated bond is carried out. For the purpose of accelerating, a photopolymerization initiator can be added. That is, after forming a desired helical structure, in order to obtain a selective reflection color having high color purity without changing the structure, it is preferable that the polymerization and curing reaction of the liquid crystal composition be rapid.

The photopolymerization initiator can be appropriately selected from known ones, for example, p-methoxyphenyl-2,4-bis (trichloromethyl) -s-triazine, 2- (p-butoxy) Styryl) -5-trichloromethyl 1,3,4-oxadiazole, 9-phenylacridine, 9,10-dimethylbenzphenazine,
Benzophenone / Michler's ketone, hexaarylbiimidazole / mercaptobenzimidazole, benzyldimethyl ketal, thioxanthone / amine and the like.

The amount of the photopolymerization initiator is preferably 0.1 to 20% by weight, more preferably 0.5 to 5% by weight, based on the weight of the solid content of the liquid crystal composition. If the amount is less than 0.1% by weight, the curing efficiency at the time of light irradiation is low, so that it may take a long time. If the amount exceeds 20% by weight, the light transmittance from the ultraviolet region to the visible light region may be required. May be inferior.

(Polymerizable monomer) A polymerizable monomer may be used in combination with the cholesteric liquid crystal composition. When the polymerizable monomer is used in combination, the distribution of the selective reflection wavelength is formed (patterned) by changing the torsional force of the liquid crystal by light irradiation, and then the helical structure (selective reflectivity) is fixed, and the liquid crystal composition after fixing is fixed. The strength of the object can be further improved.
However, when the cholesteric liquid crystal compound has an unsaturated bond in the same molecule, it is not always necessary to add.

Examples of the polymerizable monomer include monomers having an ethylenically unsaturated bond, and specific examples thereof include polyfunctional monomers such as pentaerythritol tetraacrylate and dipentaerythritol hexaacrylate. Specific examples of the monomer having an ethylenically unsaturated bond include the following compounds, but are not limited to these in the present invention.

[0055]

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The amount of the polymerizable monomer to be added is preferably 0.5 to 50% by weight based on the weight of the solid content of the liquid crystal composition. When the amount is less than 0.5% by weight,
In some cases, sufficient curability cannot be obtained, and when it exceeds 50% by weight, the alignment of liquid crystal molecules is hindered, and sufficient color formation may not be obtained.

(Other Components) Further, other components include a binder resin, a solvent, a surfactant, a polymerization inhibitor, a thickener,
Dyes, pigments, ultraviolet absorbers, gelling agents and the like can also be added. As the other components, those having excellent compatibility with the cholesteric liquid crystal compound are preferable because they affect the strength of the color filter film cured by ultraviolet curing.

If these components are movable in the cured color filter film, the released components lower the film strength and cause various changes in the characteristics of the color filter. Therefore, as the other component to be added, it is preferable to use a component having a functional group of the same type as the polymerizable functional group introduced into the cholesteric liquid crystal compound. That is, the other components are fixed in the liquid crystal compound by polymerization and curing without being released in the film, so that the film strength and various characteristics are not impaired.

Examples of the binder resin include polystyrene compounds such as polystyrene and poly-α-methylstyrene, cellulose resins such as methylcellulose, ethylcellulose and acetylcellulose; acidic cellulose derivatives having a carboxyl group in the side chain; polyvinylformal; Acetal resins such as polyvinyl butyral, JP-A-59-44615, JP-B-54-34327,
JP-B-58-12577, JP-B-54-25957
JP-A-59-53836, JP-A-59-7104
No. 8, methacrylic acid copolymer, acrylic acid copolymer, itaconic acid copolymer, crotonic acid copolymer, maleic acid copolymer, partially esterified maleic acid copolymer and the like.

The homopolymer of an alkyl acrylate and the homopolymer of an alkyl methacrylate are also exemplified. In these, the alkyl group is a methyl group, an ethyl group, an n-propyl group, an n-butyl group, an iso-alkyl group.
-Butyl group, n-hexyl group, cyclohexyl group, 2-
Examples thereof include an ethylhexyl group. In addition, a polymer having a hydroxyl group to which an acid anhydride is added, a benzyl (meth) acrylate / (homopolymer of methacrylic acid) acrylic acid copolymer or benzyl (meth) acrylate / (meth) acrylic acid / other monomer And the like.

Among the above, a binder resin containing a carboxyl group is preferable from the viewpoint of alkali developability after patterning and mass productivity. When forming a liquid crystal layer on a plastic substrate (coating, transfer, etc.), when a binder resin containing a carboxyl group is used as a binder component in a cholesteric liquid crystal composition prepared as a coating liquid,
Alkaline development is possible, and patterning can be easily performed by alkali development after light irradiation.

The content of the binder resin in the liquid crystal composition is preferably from 0 to 50% by weight, more preferably from 0 to 30% by weight. If the content exceeds 50% by weight, the orientation of the cholesteric liquid crystalline compound may be insufficient.

Further, the following components can be added. In the liquid crystal composition of the present invention, it is preferable to use a surfactant together with the photoreactive chiral agent and the cholesteric liquid crystal compound from the viewpoint of further improving the color purity of the hue that selectively reflects. Specifically, a nonionic surfactant is preferable, and a nonionic surfactant can be appropriately selected from known nonionic surfactants.

The polymerization inhibitor may be added for the purpose of improving the storage stability. Examples include hydroquinone, hydroquinone monomethyl ether, phenothiazine, benzoquinone, and derivatives thereof. The addition amount of the polymerization inhibitor is 0 to 1 with respect to the polymerizable monomer.
0% by weight is preferable, and 0 to 5% by weight is more preferable.

The content of the other components excluding the binder resin is preferably 10% by weight or less based on the total solid weight of the cholesteric liquid crystal composition. When the content exceeds 10% by weight, the strength of the color filter film cured by ultraviolet curing may be reduced.

The cholesteric liquid crystal composition can be prepared by dissolving and dispersing the above-mentioned components in an appropriate solvent, and can be used by molding it into an arbitrary shape or forming it on a support or the like. Here, as the solvent, for example, 2
-Butanone, cyclohexanone, methylene chloride, chloroform and the like.

<Cholesteric Liquid Crystal Color Filter> The cholesteric liquid crystal color filter of the present invention comprises a layer containing the above-mentioned cholesteric liquid crystal composition provided on a resin substrate. After being imagewise exposed and patterned, it is produced by a method of manufacturing a cholesteric liquid crystal color filter including at least one step of photopolymerizing and curing with a second light (hereinafter, sometimes referred to as “exposure step”). You. In addition, two or more layers containing the cholesteric liquid crystal composition can be laminated, and in this case, the exposure step is provided in a plurality of steps.

In addition, the method of manufacturing a cholesteric liquid crystal color filter includes:
Appropriately, a step of forming a liquid crystal layer by providing a liquid crystal composition on a substrate (coating step, etc.), a step of performing an alignment treatment on a contact surface with the liquid crystal composition (an alignment treatment step), and a liquid crystal composition ( (Transfer step) for transferring the liquid crystal layer). Hereinafter, the cholesteric liquid crystal color filter of the present invention will be described in detail through the description of the method of manufacturing the cholesteric liquid crystal color filter.

Hereinafter, a specific embodiment will be described as an example of a manufacturing method including the above-mentioned exposure step. -Exposure Step- In the exposure step, both patterning and fixing (polymerization curing) of the liquid crystal compound are performed by light irradiation. That is, after the photoreactive chiral agent is imagewise exposed and patterned by the first light having a wavelength sensitive to the high sensitivity, the polymerization initiator is photopolymerized by the second light sensitive to the high sensitivity. After curing, the helical structure of the liquid crystal compound is fixed to a desired selective reflection color.

When the liquid crystal composition is irradiated with the first light, the co-existing photoreactive chiral agent responds to the illuminance to change the helical structure of the liquid crystal compound. An image-like pattern is formed showing the reflection color. Therefore, if light irradiation is performed while changing the irradiation intensity for each desired region, a plurality of colors are presented in accordance with the irradiation intensity, for example, exposure is performed through an exposure mask created by changing the light transmittance like an image. Thus, an image, that is, a colored region having different selective reflection can be simultaneously formed by one light irradiation. Further, a liquid crystal color filter can be manufactured by irradiating second light and curing (fixing) the second light.

The wavelength of the first light is preferably set in the light-sensitive wavelength region of the photoreactive chiral agent, in particular, a wavelength close to the light-sensitive peak wavelength, in that sufficient patterning sensitivity can be obtained. Further, it is preferable that the wavelength of the second light be set in a light-sensitive wavelength range of the polymerization initiator, in particular, a wavelength close to the light-sensitive peak wavelength, in that sufficient photopolymerization sensitivity can be obtained. The illuminance (irradiation intensity) of the first and second lights is not particularly limited, and can be appropriately selected depending on the material to be used so that sufficient photosensitivity can be obtained during patterning and polymerization curing.

The light source used for irradiating the first and second lights is preferably a light source which emits ultraviolet light because it has a high energy and can rapidly change the structure of the liquid crystal compound and the polymerization reaction. , Metal halide lamps, Hg-Xe lamps and the like. Further, it is preferable to have a light quantity variable function.

More specifically, the manufacturing method according to the following first and second embodiments may be used, and the manufacturing method can be more suitably performed according to these two embodiments. [First Embodiment] (1) A step of providing a liquid crystal composition in a coating liquid state on a temporary support to form a transfer material having at least a liquid crystal layer. The liquid crystal composition in the coating liquid can be prepared by dissolving and dispersing each component in an appropriate solvent. Here, as the solvent, for example, 2-butanone, cyclohexanone, methylene chloride,
Chloroform and the like can be mentioned. Between the liquid crystal layer and the temporary support, a cushion layer containing a thermoplastic resin or the like may be provided from the viewpoint of ensuring adhesion during transfer, such as when there is a foreign substance or the like on the transfer target. It is also preferable that the surface of the cushion layer or the like is subjected to an orientation treatment (orientation treatment step) such as a rubbing treatment.

(2) A step of laminating the transfer material on a resin (plastic) substrate. In addition to the above substrate, an image receiving material having an image receiving layer on a plastic substrate may be used. The liquid crystal composition may be applied and formed directly on the substrate as in the second embodiment described later, but a transfer method is preferable in terms of material loss and cost. (3) A step of removing the temporary support from the plastic substrate and forming a cholesteric liquid crystal layer on the plastic substrate (transfer step). The liquid crystal layer may be formed of a plurality of layers by further laminating after the following (4).

(4) While heating the cholesteric liquid crystal layer to about 100 ° C., the illuminance ν is image-wise through an exposure mask.
A step of irradiating ultraviolet rays of ¹ to form a pixel pattern showing a selective reflection color, and further irradiating ultraviolet rays of illuminance ν ² to cure the layer (exposure step). (5) A step of removing unnecessary liquid crystal layers and the like by performing an alkali developing treatment after the exposure (processing step).

[Second Aspect] (1) A step of forming a liquid crystal layer by directly providing a liquid crystal composition on a plastic substrate constituting a color filter. Here, the liquid crystal layer can be formed by applying a liquid crystal composition prepared as a coating liquid in the same manner as described above by a known coating method using a bar coater, a spin coater or the like (coating step).
Further, an alignment film similar to the above may be formed between the cholesteric liquid crystal layer and the temporary support. The surface of the alignment film or the like is preferably subjected to an alignment treatment (alignment treatment step) such as a rubbing treatment. (2) The same exposure step and processing step as steps (4) and (5) of the first embodiment.

The thickness of the cholesteric liquid crystal color filter is preferably 1.5 to 5 μm.

Further description is made below with reference to FIGS. 1 to 3 are schematic views showing one embodiment of a process for manufacturing a liquid crystal color filter of the present invention. First, the components described above are dissolved in an appropriate solvent to prepare a coating liquid cholesteric liquid crystal composition. Here, each component and solvent are as described above.

As shown in FIG. 1- (A), a support 10 (hereinafter also referred to as a “temporary support”) is prepared, and an acrylic resin, polyester, polyurethane, or the like is applied and formed on the support 10. Cushion layer (thermoplastic resin layer) 12
And an alignment film 1 made of polyvinyl alcohol or the like.
4 is laminated. A rubbing process is performed on this alignment film as shown in FIG. This rubbing treatment is not always necessary, but the rubbing treatment can further improve the orientation. Next, FIG.
As shown in (C), a coating liquid cholesteric liquid crystal composition is applied on the alignment film 14 and dried to form a cholesteric liquid crystal layer 16, and then a cover film 18 is provided on the cholesteric liquid crystal layer 16, Create a transfer material. Hereinafter, the transfer material is referred to as a transfer sheet 20.

On the other hand, as shown in FIG. 1- (D), a resin (plastic) substrate 22 is prepared, an alignment film 24 is formed on the substrate in the same manner as described above, and the surface thereof is subjected to a rubbing treatment. . Hereinafter, this is referred to as a color filter substrate 26.

Next, after the cover film 18 of the transfer sheet 20 is peeled off, as shown in FIG. 2E, the surface of the cholesteric liquid crystal layer 16 of the transfer sheet 20 and the alignment film 24 of the color filter substrate 26 are removed. Are laminated so that they come into contact with the surface of each other, and laminated through a roll rotating in the direction of the arrow in the figure. Thereafter, as shown in FIG. 2F, the alignment film 14 of the transfer sheet 20 and the cushion layer 1 are formed.
2 and the cholesteric liquid crystal layer is transferred together with the alignment film 14 on the color filter substrate. In this case, the cushion layer 12 does not necessarily have to be peeled off together with the temporary support 10.

After the transfer, 7
The color is developed by heating to a temperature of 0 to 120 ° C. As shown in FIG. 3G, an exposure mask 28 having a plurality of regions having different light transmittances is disposed above the alignment film 14, and the first light is transmitted through the mask 28 through the cholesteric liquid crystal layer. 1
6 is irradiated in a pattern. Cholesteric liquid crystal layer 1
6 includes a liquid crystal compound, a chiral compound, or the like such that the helical pitch varies depending on the amount of light irradiation, and a structure having a different helical pitch is provided for each pattern, for example, green (G).
Are reflected, blue (B) and red (R) are transmitted, blue (B) is reflected, green (G) and red (R) are transmitted, red (R) is reflected, and green ( G) and blue (B).

Next, as shown in FIG. 3H, the cholesteric liquid crystal layer 16 is further irradiated with ultraviolet rays at an irradiation intensity different from the light irradiation in the step (G) to fix the pattern. Thereafter, unnecessary portions on the cholesteric liquid crystal layer 16 (for example, remaining portions such as a cushion layer and an intermediate layer, and unexposed portions) are removed by alkali development using 2-butanone, chloroform, or the like.
As shown in (I), a cholesteric liquid crystal layer having a BGR reflection region can be formed.

The method shown in FIGS. 1 to 3 is an embodiment of a method for manufacturing a color filter by a lamination method, but may be a method by a coating method in which a liquid crystal layer is directly formed on a color filter substrate. . In this case, when applied to the above embodiment, the cholesteric liquid crystal composition is applied on the alignment film 24 of the color filter substrate 26 shown in FIG. The steps shown in I) are sequentially performed.

These steps and the materials used for the transfer material, the support, and the like are described in Japanese Patent Application Nos. 11-342896 and 11-343665 filed by the present inventors.
The details are described in each specification of the item.

As described above, by using a resin (plastic) substrate as the cell substrate, the impact resistance can be greatly improved, and the selective reflection characteristic of the cholesteric liquid crystal is utilized, so that A cholesteric liquid crystal color filter having three primary colors of blue (B), green (G), and red (R) having excellent color purity can be obtained. Moreover,
The color filter changes the twisting power of the liquid crystal by changing the amount of light to the cholesteric liquid crystal composition and irradiating it with light.
It is obtained by forming regions having different twist structures of the liquid crystal, and can be manufactured at a low temperature of 120 ° C. or less, so that the plastic substrate does not involve warping or deformation, and the pattern is caused by the warping or deformation. Accuracy does not decrease.

[0087]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1 (1) Preparation of Filter Substrate A coating solution of polyamic acid (SE-7210, manufactured by Nissan Chemical Co., Ltd.) was applied on a plastic substrate for LCD (manufactured by Teijin Limited) using a spin coater. Then, after drying in an oven at 100 ° C. for 5 minutes, it was baked in an oven at 110 ° C. for 8 hours to form an alignment film. Further, the surface of the film was subjected to an orientation treatment by a rubbing treatment to prepare a plastic substrate with an orientation film.

(2) Formation of Filter Layer On the alignment film of the plastic substrate provided with an alignment film obtained above, a coating solution for a photosensitive resin layer prepared according to the following formulation was applied by a spin coater, and this was applied at 100 ° C. For 2 minutes to form a photosensitive resin layer.

[0090]

Embedded image

Next, the photosensitive resin layer was held on a hot plate at 110 ° C. for 5 minutes so that the photosensitive resin layer was in contact with the surface of the glass substrate, so that the photosensitive resin layer was colored. Further, on the photosensitive resin layer, the transmittance is different in three stages (0%, 46%, 92%), and the respective regions are arranged corresponding to blue pixels, green pixels, and red pixels. An ultra-high pressure mercury lamp is arranged via a photomask and a bandpass filter centered at 365 nm,
Irradiation was performed with an ultra-high pressure mercury lamp through this photomask and bandpass filter to perform patterning. The irradiation energy at this time was 300 mJ / cm ² for the red pixel.
And the irradiation intensity was 30 mW / cm ² .

Next, the photomask and the band-pass filter were removed, and the irradiation energy was 500 mJ / cm ² by using the same ultra-high pressure mercury lamp while blowing nitrogen gas.
Then, the entire surface was exposed and polymerized and cured. Further, in order to promote the degree of curing of the filter portion (photosensitive resin layer), the temperature is set
Baked in an oven for 10 hours to obtain a cholesteric liquid crystal color filter of the present invention in which red, green, and blue pixel patterns were formed. Hereinafter, this is referred to as a “liquid crystal color filter substrate”.

Using the liquid crystal color filter substrate obtained above, a layer having a thickness of 140 was formed on the surface of the liquid crystal color filter substrate on which the color filter was formed by sputtering.
An ITO film of 0 ° was formed. This is called substrate A. Further, apart from the substrate A, the same L as that used above is used.
On a plastic substrate for CD, a layer thickness of 14
An ITO film of 00 Å was formed. This is called substrate B.

For each of the substrates A and B, an ITO
A polyimide alignment film (JSR1051, manufactured by JSR) coating solution was applied on the film by a spin coater, dried in an oven at 80 ° C., and baked in an oven at 120 ° C. for 1 hour to form an alignment film. Further, the surface of the film was rubbed to obtain substrates A and B having an alignment film.

An opening serving as a liquid crystal injection port was secured on the alignment film of the substrate B, and a sealing adhesive was applied to the edge. Further, the entirety of the substrate B on the alignment film has a diameter of 4.5 μm.
m spacer particles were sprayed. Next, the substrate A is arranged on the alignment film of the substrate B on which the spacer particles are scattered so that the alignment film of the substrate A is opposed to the substrate A, and the substrates are bonded so that the rubbing directions of both alignment films are orthogonal to each other. Cell. In this cell, a cholesteric liquid crystal (ZLI508)
1, a product made by Merck Japan Ltd.)
A liquid crystal composition containing 0.1% (1, Merck Japan K.K.) was injected to prepare LCD (1).

Comparative Example 1 A pigment-dispersed glass substrate with a color filter (manufactured by Toppan Printing Co., Ltd.) was prepared, and a layer having a thickness of 1400 mm was formed on the surface of the glass substrate on which the color filter was formed by sputtering. An ITO film was formed.
This is called substrate C. Further, an ITO film having a layer thickness of 1400 ° was formed on a glass substrate for LCD (manufactured by Corning Japan KK) in the same manner as described above. This is called substrate D.

For each of the substrates C and D, an ITO
A polyimide alignment film (JSR1051, manufactured by JSR) coating solution was applied on the film by a spin coater, dried in an oven at 80 ° C., and baked in an oven at 120 ° C. for 1 hour to form an alignment film. Further, the surface of the film was subjected to a rubbing treatment to obtain substrates C and D having an alignment film.

An opening serving as a liquid crystal injection port was secured on the alignment film of the substrate D, and a sealing adhesive was applied to the edge. In addition, the entirety of the substrate D on the alignment film has a diameter of 4.5 μm.
m spacer particles were sprayed. Next, the substrate C is disposed on the alignment film of the substrate D on which the spacer particles are scattered such that the alignment film of the substrate C is opposed to the substrate C, and the substrates are bonded so that the rubbing directions of both alignment films are orthogonal to each other. Cell. In this cell, a cholesteric liquid crystal (ZLI508)
1, a product made by Merck Japan Ltd.)
A liquid crystal composition containing 0.1% (1, Merck Japan K.K.) was injected to produce LCD (2).

Comparative Example 2 A plastic substrate with an electrodeposition type color filter (manufactured by Nippon Paint Co., Ltd.) was prepared, and a layer having a thickness of 1400 mm was formed on the surface of the plastic substrate on which the color filter was formed by sputtering. An ITO film was formed. This is called substrate E. On the plastic for LCD (manufactured by Teijin Limited) used in Example 1, an ITO film having a layer thickness of 1400 Å was formed in the same manner as described above. This is referred to as a substrate F.

For each of the substrates C and D, an ITO
A polyimide alignment film (JSR1051, manufactured by JSR) coating solution was applied on the film by a spin coater, dried in an oven at 80 ° C., and baked in an oven at 120 ° C. for 1 hour to form an alignment film. Further, the surface of the film was subjected to a rubbing treatment to obtain substrates C and D having an alignment film.

An opening serving as a liquid crystal injection port was secured on the alignment film of the substrate F, and a sealing adhesive was applied to the edge. In addition, the entirety of the substrate F on the alignment film has a diameter of 4.5 μm.
m spacer particles were sprayed. Next, the substrate E is disposed on the alignment film of the substrate F on which the spacer particles are dispersed, such that the alignment film of the substrate E is opposed to the alignment film, and the substrates are bonded so that the rubbing directions of both alignment films are orthogonal to each other. Cell. In this cell, a cholesteric liquid crystal (ZLI508)
1, a product made by Merck Japan Ltd.)
A liquid crystal composition containing 0.1% (1, Merck Japan K.K.) was injected to prepare LCD (3).

<Evaluation of LCD> LCD obtained from above
(1) to (3) were evaluated as follows. The results of the evaluation are shown in Table 1 below. (Drop strength) For each of the LCDs (1) to (3), the size was set to a substrate thickness of 0.4 mm and 50 × 50 mm.
A height h at which a breakage rate of 30% or more when ten pieces were dropped from a height h (mm) on a flat stone bed was determined, and this was used as an index indicating the drop strength.

(Color Purity) The color of each LCD was measured as follows using a chromaticity meter OSP-200 (manufactured by Olympus Corporation). LCD red (R), green (G), blue (B)
Are individually microscopically measured, and the x, y coordinates CIE1931 of each color are measured.
Plotted on the specified coordinates, was a triangle that can be when connecting the RGB each point and the color reproduction area S _n. Here, when the color reproduction area S ₀ defined by the NTSC standard and 100, measured values S ₁ and each of LCD (1) ~ (3) with respect to the S _0,
The ratio [%] of S ₂ and S ₃ was defined as NTSC ratio.

(Brightness) In the same manner as in the evaluation of the color purity,
The red (R), green (G), and blue (B) colors of the LCD are individually microscopically measured with a chromaticity meter OSP-200 (manufactured by Olympus Corporation), and the Y values of the three RGB colors are averaged. The WBY value was determined as an index indicating the luminance.

[0105]

[Table 1]

From the results shown in Table 1, the LCD (1) comprising a plastic substrate and provided with the cholesteric liquid crystal color filter of the present invention utilizing selective reflection of liquid crystal has a high breaking strength against drop impact and a high color purity. It was extremely excellent and also excellent in luminance. On the other hand, in the conventional LCD (2) using a glass substrate, not only sufficient strength was not obtained, but also the color purity was poor. The LCD (3), which is made of a plastic substrate and has a color filter formed by an electrodeposition method, has the same strength as the LCD (1), but has extremely low color purity.
It was inferior to (2). Also, the luminance was low.

[0107]

According to the present invention, an LCD using a resin cell is provided.
The present invention can provide a cholesteric liquid crystal color filter which is suitably used, is made of a resin (plastic) substrate (cell substrate), has excellent impact resistance, and has excellent color purity. Further, it is possible to provide a low-cost cholesteric liquid crystal color filter which can be easily formed on a resin substrate (cell substrate) at a low temperature of 120 ° C. or lower without any trouble such as deformation of the substrate.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a part of a step of manufacturing a cholesteric liquid crystal color filter of the present invention.

FIG. 2 is a schematic view showing a part of a step of manufacturing a cholesteric liquid crystal color filter of the present invention.

FIG. 3 is a schematic view showing a part of a step of manufacturing a cholesteric liquid crystal color filter of the present invention.

[Explanation of symbols]

 Reference Signs List 10 support (temporary support) 12 cushion layer (thermoplastic resin layer) 14, 24 alignment film 16 liquid crystal layer (cholesteric liquid crystal composition) 20 transfer sheet 22 resin (plastic) substrate 26 color filter substrate 28 exposure mask

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // G03F 7/027 502 G03F 7/027 502 2H097 7/40 501 7/40 501 F-term (Reference) 2H025 AA13 AB13 AB20 AC01 AD01 BC13 BC83 CB51 DA18 FA06 FA12 2H048 AA06 AA09 AA18 AA22 BA03 BA04 BA16 BA64 BA66 BB15 BB42 2H090 JB03 JD13 JD17 LA15 2H091 FA02Y FB02 FC10 FC23 GA01 LA02 LA11 LA12 2H092 A27 FA12A30 FAA LA12

Claims (4)

[Claims] 1. A cholesteric liquid crystal color filter comprising a resin substrate and a layer containing a cholesteric liquid crystal composition provided thereon. 2. The composition according to claim 1, wherein the cholesteric liquid crystal composition comprises at least one polymerizable cholesteric liquid crystal compound, at least one photoreactive chiral compound, and at least one polymerization initiator. Cholesteric liquid crystal color filter. 3. The cholesteric liquid crystal color filter according to claim 1, wherein the polymerizable cholesteric liquid crystal compound has a functional group which is polymerized and cured in response to ultraviolet rays in the same molecule. 4. A method comprising the steps of: patterning a cholesteric liquid crystal composition provided on a resin substrate by imagewise exposing with a first light, photopolymerizing with a second light, and curing. The cholesteric liquid crystal color filter according to any one of claims 1 to 3, which is obtained by a method for producing a cholesteric liquid crystal color filter.